Analysis of deoxynivalenol and deoxynivalenol-3-glucosides content in Canadian spring wheat cultivars inoculated with Fusarium graminearum

Contamination of wheat grains with Fusarium mycotoxins and their modified forms is an important issue in wheat industry. The objective of this study was to analyse the deoxynivalenol (DON) and deoxynivalenol-3-glucosides (D3G) content in Canadian spring wheat cultivars grown in two locations, inoculated with a mixture of 3-acetyldeoxynivalenol (3-ADON)-producing Fusarium graminearum strains and a mixture of 15-acetlyldeoxynivalenol (15-ADON)-producing F. graminearum strains. According to the analysis of variance, significant differences were observed among the cultivars for Fusarium head blight (FHB) disease index, Fusarium-damaged kernel percentage (%FDK), DON content and D3G content. When the effect of chemotype was considered, significant differences were observed for FHB disease index, FDK percentage and DON content. The D3G content and D3G/DON ratio were not significantly different between the chemotypes, except for D3G content at the Winnipeg location. The Pearson correlation coefficient between DON and D3G was 0.84 and 0.77 at Winnipeg and Carman respectively. The highest D3G/DON ratio was observed in cultivars Carberry (44%) in Carman and CDC Kernen (63.8%) in Winnipeg. The susceptible cultivars showed lower D3G/DON ratio compared with the cultivars rated as moderately resistant and intermediate. The current study indicated that Canadian spring cultivars produce D3G upon Fusarium infection.     

Less Fusarium infestation and mycotoxin contamination in organic than in conventional cereals

A total of 602 samples of cereals, consisting of organically and conventionally produced barley, oats and wheat, were collected at harvest during 2002–2004 in Norway. Organic and conventional cereals were sampled in comparable numbers regarding cereal species, localisation and harvest time, and analysed for Fusarium mould and mycotoxins. Fusarium infestation and mycotoxin content were dependent on cereal species and varied year-by-year. However, in all cereal species, Fusarium infestation and levels of important mycotoxins were significantly lower when grown organically than conventionally. Concerning the most toxic trichothecenes, HT-2 and T-2 toxin, lower concentrations were found in organic oats and barley. Wheat was not contaminated by HT-2 and T-2, but lower concentrations of deoxynivalenol (DON) and moniliformin (MON) were found when organically produced. For mycotoxins considered to constitute the main risk to humans and animals in Norwegian cereals, i.e. HT-2 in oats and DON in oats and wheat, the median figures (mean levels in brackets) were as follows: HT-2 in organic and conventional oats were <20 (80) and 62 (117) µg/kg, DON in organic and conventional oats were 24 (114) and 36 (426) µg/kg, and DON in organic and conventional wheat were 29 (86) and 51 (170) µg/kg, respectively. Concentrations of HT-2 and T-2 in the samples were strongly correlated (r = 0.94). Other mycotoxins did not show a significant correlation to each other. Both HT-2 and T-2 concentrations were significantly correlated with infestation of F. langsethiae (r = 0.65 and r = 0.60, respectively). Concentrations of DON were significantly correlated with F. graminearum infestation (r = 0.61). Furthermore, nivalenol (NIV) was significantly correlated with infestation of F. poae (r = 0.55) and MON with F. avenaceum (r = 0.37). As lower Fusarium infestation and mycotoxin levels were found in organic cereals, factors related to agricultural practice may reduce the risk of contamination with Fusarium mycotoxins. Studies of these issues will be presented separately.     

Mycoflora and deoxynivalenol in whole wheat grains (Triticum aestivum L.) from Southern Brazil

The fungal species Fusarium graminearum is related to deoxynivalenol (DON) formation. The aim of this study was to evaluate mycoflora and DON occurrence in 53 whole wheat grain samples collected in Southern Brazil during the 2012 crop. Wheat grains showed adequate values of water activity ranging from 0.48 to 0.72, within the required limits of moisture content, ranging from 9.1% to 13.9%. In addition, low counts of fungal colonies, ranging from 10 to 8.2 × 10², were found. For Fusarium genera, there was predominance of Fusarium verticillioides (34%) and F graminearum (30.2%). For Aspergillus species, 37.7% of Aspergillus flavus was determined. Regarding the Penicillium species, Penicillium digitatum (49%) was the most found species. DON was detected in 47.2% (25 out of 53) of the samples analysed, with levels ranging from 243.7 to 2281.3 µg kg^?1 (mean: 641.9 µg kg^?1).     

Assessment of Fusarium infection in wheat heads using a quantitative polymerase chain reaction (qPCR) assay

The accuracy of a quantitative polymerase chain reaction assay in quantifying the DNA of trichothecene-producing F. culmorum and F. graminearum within harvested wheat grains and head tissue was evaluated in comparison with incidences of infected kernels and deoxynivalenol levels. In a first experiment, six durum and bread wheat varieties were grown in randomized plots for a 2-year period, and inoculated with Fusarium macroconidia at six growth stages between heading and dough ripening, to obtain a wide range of Fusarium head blight incidences. There was a close relationship between fungal DNA and the amount of deoxynivalenol, and this relationship was consistent over Fusarium species, wheat species and varieties, and over a wide range of Fusarium head blight infection. In a second experiment potted wheat plants were grown under environmentally controlled conditions and inoculated with the two Fusarium species at full flowering; head samples were collected before inoculation and after 6 h to 12 days, and processed by the quantitative polymerase chain reaction assay. This assay made it possible to detect the dynamic of fungal invasion in planta after infection had occurred, and to single out the presence of infection before the onset of the disease symptoms: A robust detection of the infection occurred within 18-24 h for F. culmorum, and within 2-9 days for F. graminearum.     

Fusarium head blight and associated mycotoxin occurrence on winter wheat in Luxembourg in 2007/2008

Fusarium head blight (FHB) is among the major causes of reduced quality in winter wheat and its products. In addition, the causal fungi produce a variety of toxins. A relatively high FHB infection rate in winter wheat was observed in 2007 and 2008 in Luxembourg. A fusariotoxin survey was carried out in 17 different geographical locations. Three groups of Fusarium mycotoxins (trichothecenes A and B and zearalenone) were analysed by a multi-detection HPLC–MS/MS method. Fusarium strains were also investigated by morphological and molecular methods. In addition, questionnaires relating to cultural practices were sent to the farmers managing the 17 fields investigated. FHB prevalence ranged from 0.3 to 65.8% (mean: 8.5%) in 2007 and from 0 to 24.5% (mean: 8.3%) in 2008. Results of morphological and molecular identification showed that the most common species isolated from diseased wheat spikes was F. graminearum (33.1%), followed by F. avenaceum (20.3%) and F. poae (17.8%). The chemical analysis revealed that 75% of the investigated fields were contaminated by deoxynivalenol (DON, range 0–8111 µg/kg). The preceding crop was highly and significantly correlated to the number of grains infected and had a significant impact on disease prevalence (p = 0.025 and 0.017, respectively, Fisher's F-test). A trend was found for maize as the preceding crop (p = 0.084, Tukey's test) to predict the amount of DON in the fields. This is the first report on the occurrence of DON and ZON in naturally infected wheat grains sampled from Luxembourg.     

Contaminants in organically and conventionally produced winter wheat (Triticum aestivum) in Belgium

A database has been compiled with the levels of important contaminants (mycotoxins, heavy metals and pesticides) measured from 2002 to 2005 in winter wheat (Triticum aestivum) grown in Belgium according to the organic and conventional farming systems. Assuming no further change in contaminant levels during cereal processing and during the preparation of foodstuffs, conservative intakes are estimated for the consumers of cereal-based products such as flour, bread, breakfast cereals, dough and pastry. The results show that for the consumer of organic foodstuffs, estimated daily intakes are 0.56 µg deoxynivalenol (DON), 0.03 µg zearalenone (ZEA), 0.19 µg Cd, 0.28 µg Pb and 0.0006 µg Hg kg^-1 body weight, taking into account the average contaminant levels in unprocessed grains and the average cereal products consumptions in Belgium. For the consumers of conventional foodstuffs, the corresponding estimated daily intakes are 0.99 µg DON, 0.06 µg ZEA, 0.17 µg Cd, 0.12 µg Pb and 0.0007 µg Hg kg^-1 body weight. In addition, it appears that for the consumers of conventional products, intakes of some post-harvest insecticides have to be taken into account (0.11 µg chlorpyriphos-methyl, 0.2 µg dichlorvos and 0.24 µg pirimiphos-methyl kg^-1 bw). When expressed as a percentage of the tolerable/acceptable daily intake (TDI/ADI), it seems that the corresponding estimated (conservative) intakes are the highest for DON (56% for organic and 99% for conventional cereal products), ZEA (16% for organic and 32% for conventional cereal products), and Cd (19% for organic and 17% for conventional cereal products), all other estimated intakes of contaminants (including pesticides) being lower than 10% of the TDI/ADI.     

Distribution of toxigenic Fusarium spp. and mycotoxin production in milling fractions of durum wheat

A reliable and sensitive PCR assay to specifically detect trichothecene-producing Fusarium spp. in milling fractions and kernel tissue of naturally infected durum wheat is reported. Assays were based on a combination of primers derived from the trichodiene synthase and the β-tubulin genes. The occurrence of toxigenic Fusarium spp. in semolina and wheat tissue (grain ends, crease, pericarp, aleurone layer, germ and albumen) was detected, even for a weakly contaminated wheat sample. Penetration of toxigenic Fusarium spp. into the interior of durum wheat kernel was demonstrated for the Nefer variety, indicating that none of the tissue structures within the wheat kernel acted as an effective barrier to fungal invasion. Moreover, after inoculation by toxigenic Fusarium strains, semolina was shown to allow high yields of trichothecenes, while bran was demonstrated to contain biochemical inhibitors able to significantly reduce trichothecene production. These results will be useful in improving breeding strategies to control trichothecene contamination of durum wheat kernels.     

Relationship between free glutathione content and quality assessment parameters of wheat cultivars (Triticum aestivum L.)

Freshly milled flour samples from ten cultivars of bread wheat were analysed for free reduced glutathione (GSH) and oxidised glutathione (GSSG) by an enzymic method. Dough rheological properties for each flour were assessed by standard Brabender techniques. Flour quality differences were also measured by Pelshenke fermentation and Zeleny sedimentation techniques. Reduced glutathione levels were negatively correlated with oxidised glutathione levels, Farinogram mixing tolerance, Extensogram resistance, Pelshenke time and Zeleny volume. The ratios of oxidised to reduced glutathione (GSSG: GSH) were positively correlated with all dough and flour quality parameters, except Extensogram extensibility. It is concluded that there are differences in the endogenous contents of reduced and oxidised glutathione between flour samples from ten cultivars of wheat. These differences may contribute significantly to variations in the quality assessment parameters established between cultivars in this study.     

Investigations on Fusarium spp. and their mycotoxins causing Fusarium ear rot of maize in Kosovo

After wheat, maize (Zea mays L.) is the second most important cereal crop in Kosovo and a major component of animal feed. The purpose of this study was to analyse the incidence and identity of the Fusarium species isolated from naturally infected maize kernels in Kosovo in 2009 and 2010, as well as the mycotoxin contamination. The disease incidence of Fusarium ear rot (from 0.7% to 40% diseased ears) on maize in Kosovo is high. The most frequently Fusarium spp. identified on maize kernels were Fusarium subglutinans, F. verticillioides/F. proliferatum and F. graminearum. Maize kernel samples were analysed by LC-MS/MS and found to be contaminated with deoxynivalenol (DON), DON-3-glucoside, 3-acetyl-DON, 15-acetyl-DON, zearalenone, zearalenone-14-sulphate, moniliformin, fumonisin B₁ and fumonisin B₂. This is the first report on the incidence and identification of Fusarium species isolated from naturally infected maize as well as the mycotoxin contamination in Kosovo.     

Trichothecene and beauvericin mycotoxin production and genetic variability in Fusarium poae isolated from wheat kernels from northern Italy

The importance and widespread incidence of Fusarium poae as a natural contaminant of wheat in different climatic areas warrants investigation into the genetic diversity and toxin profile of a northern Italy population. Eighty-one strains of F. poae isolated from durum wheat kernels, identified by species-specific polymerase chain reaction and translation elongation factor-1α gene sequence analysis, were genetically characterized by the amplified fragment length polymorphism (AFLP) technique and analysed by high-pressure liquid chromatography for their ability to produce the beauvericin (BEA) and trichothecene mycotoxins. A high level of variability was observed by using AFLP analyses, with the lowest level of genetic similarity among the strains being approximately 61%. Most of the strains, 95%, produced BEA at <2655 µg g^?1; 88% produced the trichothecene nivalenol at <865 µg g^?1 and 76% produced the trichothecene fusarenon-X at <167 µg g^?1. These data show that F. poae can produce high amounts of BEA together with trichothecenes, and can represent a high potential mycotoxin risk in Italy for wheat colonized by this species.     

Varietal differences in amino acid composition of wheat (Triticum aestivum L) grain

The differences in the amino acid composition of the developing grain between the three winter wheat (Triticum aestivum L) varieties Splendeur, Hobbit and Maris Huntsman were analysed in a growth-room experiment. At 15 days after anthesis, Maris Huntsman, the variety with the fastest leaf senescence, had a larger proportion of glutamate and smaller levels of threonine, glycine, alanine, valine, methionine and isoleucine in the total amino acid fraction; at later dates these differences were in general less pronounced, particularly compared with Splendeur. This suggests that, in the variety with the fastest leaf senescence, rapid gliadin synthesis in the grain occurs earlier. At any given percentage of nitrogen in the mature grain, Hobbit had a smaller proportion of glutamate and greater proportions of lysine, arginine and alanine; Splendeur, the only bread-making variety, had smaller levels of aspartate and lysine; and Maris Huntsman had the greatest relative amount of phenylalanine. The possible differences among the varieties in the relative proportion of some protein fractions are discussed. Until 25 days after anthesis Maris Huntsman had smaller relative proportions of free alanine, valine, leucine, isoleocine and threonine, in particular when compared with Splendeur. In Maris Huntsman, the relative amount of aspartate increased from 15 days after anthesis onwards, whereas in Hobbit it only did so in mature grains.     

Formation of fumonisins and other secondary metabolites by Fusarium oxysporum and F. proliferatum: a comparative study

The principal aim of this study was to estimate the formation of fumonisins (FB₁ and FB₂), moniliformin (MON), and ergosterol (ERG) by Fusarium oxysporum and Fusarium proliferatum, while the formation of beauvericin (BEA) was estimated by the latter Fusarium species only. Moreover, the effect of temperature on the biosynthesis of mycotoxins was also evaluated. Fumonisins were formed by F. proliferatum, with the highest yield at 18°C (720.0–1976.6 µg g^?1 for FB₁, 74.2–670.8 µg g^?1 for FB₂) and only by three of four F. oxysporum strains at a very low level (0.02–4.77 µg g^?1 for FB₁, 0.02–2.15 µg g^?1 for FB₂). The amount of MON formed by F. proliferatum was the highest (p < 0.001) at 32°C (3056.87 µg g^?1), while MON biosynthesis by F. oxysporum was lower 227.54 µg g^?1 (p < 0.001). BEA was produced by F. proliferatum with the highest level at 25°C (p < 0.001). ERG–recognized as an indicator of fungal biomass development and as a consequence of mycotoxin formation–was found at the highest concentration at a biosynthesis temperature of 25°C for F. proliferatum and F. oxysporum (p < 0.001).     

Relationship between environmental factors,dry matter loss and mycotoxin levels in stored wheat and maize infected with Fusarium species

This study examined the relationship between storage environmental factors (water activity (a _w) (0.89–0.97) and temperature (15°C–30°C)), colonisation of wheat and maize by Fusarium graminearum and F. verticillioides respectively and the dry matter losses (DMLs) caused and quantified by contamination with deoxynivalenol (DON), zearalenone (ZEA) and fumonisins (FUMs) during storage. Fungal growth was assessed by the amount of CO₂ produced under different interacting conditions of a _w and temperature. DMLs were quantified using the cumulative CO₂ data, and these were shown to increase as temperature and a _w increased. The amount of DON, ZEA (wheat for human consumption) and FUMs (feed maize) produced was significantly affected by the storage conditions. The three toxins however showed different patterns of production. Optimum for DON was at the wettest conditions (0.97a _w) and the highest temperature assessed (30°C), whereas for ZEA this shifted to 25°C. FUMs were produced in higher amounts in maize at 30°C and 0.97a _w; however, at intermediate a _w levels (0.955a _w), the highest production occurred at 25°C followed by 20°C. Polynomial models were developed for the effect of the storage factors on DMLs and toxin production. DMLs under different environmental conditions were significantly correlated with DON and FUMs. DON contamination was above the EU limits in at least 80% of the wheat samples with DMLs >1%, whereas at least 70% of the same samples contained ZEA above the respective EU legislative limits. Similarly, at least 75% of the maize samples with DMLs?≥?0.9% exceeded the EU limits for the sum of FUMs in feed. These results show that it may be possible to use temporal CO₂ production during storage of grains as an indicator of the level of contamination of the grain with mycotoxins.     

Impact of post-anthesis rainfall,fungicide and harvesting time on the concentration of deoxynivalenol and zearalenone in wheat

Field experiments were conducted to identify the impact of post-anthesis rainfall on the concentration of deoxynivalenol (DON) and zearalenone (ZON) in harvested wheat grain. Winter wheat plots were inoculated with Fusarium graminearum at stem extension (GS31) and prothioconazole was applied at mid-anthesis (GS65) to split plots and plots were subsequently mist irrigated for 5 days. Plots were either covered by polytunnels, irrigated by sprinklers or left as non-irrigated uncovered control plots after medium-milk (GS75). Plots were harvested either when ripe (GS92; early harvest) or three weeks later (late harvest). Fusarium head blight (FHB) was assessed each week from inoculation. At harvest, yield and grain quality was measured and grains were analysed for DON and ZON. Differences in rainfall resulted in contrasting disease pressure in the two experiments, with low FHB in the first experiment and high FHB in the second. Difference in FHB resulted in large differences in grain yield, quality and mycotoxin content. DON concentration was significantly (P < 0.05) higher in irrigated compared to covered and control plots in the first experiment, whereas in the second experiment, DON was significantly (P < 0.05) higher in the covered plots compared to the control and irrigated plots. ZON concentration was significantly (P < 0.05) higher in irrigated plots in both experiments. Later harvesting resulted in an approximate fivefold increase in ZON in the first experiment, but was not significantly different in the second experiment. Prothioconazole significantly (P < 0.05) reduced DON in both experiments, but gave inconsistent reductions to ZON. This is the first report to show that the post-anthesis rainfall can significantly increase ZON in wheat, which can increase further with a delayed harvest but may be significantly reduced with the application of prothioconazole. Importantly, in the absence of moisture late season, ZON remains at very low concentrations even when wheat is severely affected by FHB.     

Development of simple and efficient in Planta transformation method for wheat (Triticum aestivum L.) using Agrobacterium tumefaciens

Wheat (Triticum aestivum L. var. Shiranekomugi) seeds were soaked in water at 22 degrees C for 1 d. Thereafter, the embryo of the soaked seeds was inoculated with Agrobacterium tumefaciens by piercing a region of the embryonic apical meristem with a needle that had been dipped in an A. tumefaciens inoculum. The inoculated seeds were incubated at 22 degrees C for 2 d and sterilized by cefotaxime (Claforan) (1000 ppm water solution) treatment and then vernalized at 5 degrees C for 25 d. Finally, the seedlings were grown to maturation (T(0) plants) and allowed to pollinate naturally for seed setting (T(1) plants) in pots under nonsterile condition. To examine the transformation by various means, four different strains of A. tumefaciens were used for transformation. The following five lines of evidence proved the transformation: altered phenotype and its transmittance to the next generation, resistance of T(1) seed germination to geneticin or hygromycin B, the detection of a transgene in T(1) plants by PCR analysis and Southern hybridization and the rescue of the plasmid consisting of the integrated T-DNA and flanking wheat genome DNA from T(1) plants. The transformation efficiency of T(1) plants, which were transformed using different A. tumefaciens strains, was estimated to be 33% by PCR analysis, 75% by Southern hybridization and 40% by plasmid rescue.     

Associations of planting date,drought stress,and insects with Fusarium ear rot and fumonisin B1 contamination in California maize

Fusarium ear rot, caused by Fusarium verticillioides, is one of the most common diseases of maize, causing yield and quality reductions and contamination of grain by fumonisins and other mycotoxins. Drought stress and various insects have been implicated as factors affecting disease severity. Field studies were conducted to evaluate the interactions and relative influences of drought stress, insect infestation, and planting date upon Fusarium ear rot severity and fumonisin B₁ contamination. Three hybrids varying in partial resistance to Fusarium ear rot were sown on three planting dates and subjected to four irrigation regimes to induce differing levels of drought stress. A foliar-spray insecticide treatment was imposed to induce differing levels of insect injury. Populations of thrips (Frankliniella spp.), damage by corn earworm (Helicoverpa zeae), Fusarium ear rot symptoms, and fumonisin B₁ levels were assessed. There were significant effects of hybrid, planting date, insecticide treatment, and drought stress on Fusarium ear rot symptoms and fumonisin B₁ contamination, and these factors also had significant interacting effects. The most influential factors were hybrid and insecticide treatment, but their effects were influenced by planting date and drought stress. The more resistant hybrids and the insecticide-treated plots consistently had lower Fusarium ear rot severity and fumonisin B₁ contamination. Later planting dates typically had higher thrips populations, more Fusarium ear rot, and higher levels of fumonisin B₁. Insect activity was significantly correlated with disease severity and fumonisin contamination, and the correlations were strongest for thrips. The results of this study confirm the influence of thrips on Fusarium ear rot severity in California, USA, and also establish a strong association between thrips and fumonisin B₁ levels.     

Fusarium infection of maize and maize-based products and exposure of a rural population to fumonisin B1 in Limpopo Province,South Africa

Fusarium species (spp.) and fumonisin B₁ (FB₁) contaminations were monitored in maize and porridge consumed by a rural population of Limpopo Province, South Africa. Faecal samples were also analysed for FB₁ as a means of estimating the degree of dietary exposure to this mycotoxin. In total, 142 samples of maize (n?=?54), porridge (47) and faeces (41) were screened for Fusarium spp. using a serial dilution technique followed by DNA sequencing, while FB₁ was further screened and quantified by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), respectively. At least four species of Fusarium were identified, of which F. verticillioides was the most prevalent in all three sample types analysed. The contamination levels of FB₁ were significantly higher in 87% of maize sampled (range?=?101–53,863?µg?kg^?1) as compared with porridge (74% incidence rate; range?=?0.2–20?µg?kg^?1) and faecal samples (100% incidence rate; range?=?0.3–464?µg?kg^?1). Thus, it can be deduced that the level of human exposure to FB₁ via the consumption of maize was high as several samples contained levels exceeding 1000?µg?kg^?1, which was strongly supported by the levels found in faecal samples. Further data revealed that a high proportion of FB₁ is destroyed or removed by processing maize into porridge. As maize porridge is consumed as a staple, the low levels found provide a means to limit exposure to FB₁. Levels of FB₁ found in the faeces which were higher indicate that other foods contaminated with the toxin are also consumed.     

Fumonisin B1 and B2 occurrence in dried fig fruits (Ficus carica L.) under Meander Valley's climatic conditions and relationship with fruit quality

Fusarium is the agent causing endosepsis (internal rot) in fig fruits and it is widespread in fig orchards in the Aegean region. This research was conducted to determine the natural occurrence of fumonisin B₁ (FB₁) and B₂ (FB₂) on dried fig fruits of Sarilop (syn. Calimyrna) variety which are mainly grown in the Big and Small Meander Basins in the Aegean region, representing 60% of world dried fig production. A total of 262 samples belonging to two quality classes, Class A and Class cull, were collected from 12 different locations during the two crop years in 2004 and 2005. The fumonisin detection method is based on extraction with methanol–acetonitrile–water, derivatization with o-phthaldehyde and quantification by reversed-phase high-performance liquid chromatography with fluorescence detection. The mean concentrations of FB₁ and FB₂ in fumonisin-positive samples were 0.080?±?0.047?µg?g^?1 and 0.055?±?0.031?µg?g^?1 and ranged from LOD to 0.332?µg?g^?1 and from LOD to 0.198?µg?g^?1, respectively. The incidence of fumonisins significantly differed between the two crop years. This difference can be attributed to the alteration in the rainfall regime from mid-May to mid-August (7.2?mm in 2004, 90.9?mm in 2005) and number of humid wind currents from a westerly direction (183 in 2004, 492 in 2005) from the end of July and mid-August that may have triggered a higher incidence of Fusarium spp. and thus fumonisin production.     

Analysis of fumonisin contamination and the presence of Fusarium in wheat with kernel black point disease in the United States

The ability of the fungus Fusarium proliferatum to cause kernel black point disease in wheat was previously established, but natural contamination of black point wheat with both F. proliferatum and fumonisin mycotoxins has not been studied in the United States. Low levels of fumonisins were detected in nine of 43 wheat samples with kernel black point disease that were obtained from across the United States. A subset of samples was contaminated with F. proliferatum as well as with F. fujikuroi, F. nygamai, F. thapsinum and F. verticillioides, species closely related to F. proliferatum and morphologically similar to it in that they produce chains of asexual spores, or conidia. Nevertheless, of conidial chain-forming fusaria isolated from symptomatic wheat, F. proliferatum dominated. In greenhouse tests, isolates of F. proliferatum and the other species recovered from wheat samples were able to cause symptoms of kernel black point and, in some cases, low levels of fumonisin contamination of wheat. These data add to the understanding of the risk of fumonisin contamination of wheat and the potential for Fusarium species to cause kernel black point disease and fumonisin contamination of wheat. Further, the results of this study indicate that while US-grown wheat can sporadically be contaminated by fumonisins, the natural contamination levels seem to be low. The observations made provide evidence that fumonisins are not likely to be a factor contributing to the ability of Fusarium to cause kernel black point disease.     

Influence of inoculum and climatic factors on the severity of Fusarium head blight in German spring and winter barley

Fusarium head blight (FHB) of small cereals is a disease of global importance with regard to economic losses and mycotoxin contamination harmful to human and animal health. In Germany, FHB is predominantly associated with wheat and F. graminearum is recognised as the major causal agent of the disease, but little is known about FHB of barley. Monitoring of the natural occurrence of FHB on Bavarian barley revealed differences for individual Fusarium spp. in incidence and severity of grain infection between years and between spring and winter barley. Parallel measurement of fungal DNA content in grain and mycotoxin content suggested the importance of F. graminearum in winter barley and of F. langsethiae in spring barley for FHB. The infection success of these two species was associated with certain weather conditions and barley flowering time. Inoculation experiments in the field revealed different effects of five Fusarium spp. on symptom formation, grain yield and mycotoxin production. A significant association between fungal infection of grain and mycotoxin content was observed following natural or artificial infection with the type B trichothecene producer F. culmorum, but not with the type A trichothecene-producing species F. langsethiae and F. sporotrichioides. Trichothecene type A toxin contamination also occurred in the absence of significant damage to grain and did not necessarily promote fungal colonisation.